Those skilled in the art of diagnosing cardiac ailments have long understood that certain patients, in particular heart failure (HF) patients, suffer uncoordinated mechanical activity wherein the myocardial depolarization and contraction of the right and left ventricle do not occur simultaneously. Such uncoordinated motion causes a decrease in cardiac output (CO), among other detrimental effects. Recently a variety of techniques have been proposed and practiced for minimizing such uncoordinated motion and increasing CO.
These prior art techniques for minimizing ventricular uncoordinated motion include CRT. In some forms of CRT, pressure-based measurements in one or both ventricles have been known and used for some time. In such methods, a pressure transducer is typically coupled to the distal end of a medical electrical lead used to measure intraventricular pressure variations. Such measured variations (maximum, minimum, calculated first derivatives thereof, etc.) provide feedback to an implantable pulse generator (IPG) programmed to deliver CRT. Such an IPG typically includes at least three medical electrical leads coupled to cardiac tissue. A first lead typically coupled to the right atrium, a second lead typically coupled to the right ventricle, and a third lead typically coupled to the left ventricle (often via the coronary sinus or great vein). That is, the third lead often couples to a location on the free wall of the left ventricle.
Thus, as is known in the art, based at least in part on the pressure-based measurements the IPG provides electrical cardiac pacing stimulus to the left ventricle (LV) and the right ventricle (RV) in an effort to suitably increase the measured pressure(s) and/or derivatives thereof.
When successfully delivered, CRT is known to increase CO and may, over time, cause a phenomenon known in the art as “reverse remodeling” of the LV and RV (and/or other beneficial) physiologic changes to the patient's heart.
The inventors are also aware of another technique for CRT for HF patients; namely, using an accelerometer disposed in the apex of the right ventricle to measure endocardial acceleration of the apical portion of the right ventricle. From this measurement in the right ventricle a left ventricular activity is inferred. However, to the best knowledge of the inventors such technique has not been used to directly measure deflection of the ventricular or atrial septal wall in patients afflicted with uncoordinated ventricular motion and the like.